This invention relates to a process for preparing a polyphenylene ether capable of having optional number of a reactive functional group(s) in a molecule, which functional group is capable of physically or chemically binding different kinds of polymers.
More specifically, it relates to a process for preparing various kinds of modified polyphenylene ethers composed of reacting a polyphenylene ether having optional number of a carbon-carbon unsaturated bond with various kinds of functionalizing agent.
When preparing a polymer blend, a polyphenylene ether (hereinafter abbreviated to as "PPE") is generally incompatible with other resins except for specific resins and has poor affinity. Thus, when two components of PPE and the other resin are simply mixed, phase separation structure which is stable in energy is shown so that adhesiveness at interface of the two phase structure is not so good. Therefore, mechanical strength and impact resistance are lowered and serious problems of causing delamination easily at molding, etc. are shown.
In order to solve the above problems, it is effective to use a blocked material or grafted material comprising a segment having affinity to both PPE and a polymer to be blended, as a compatibilizing agent. For synthesizing them, there are cases where a bifunctional small molecule such as maleic anhydride is used as a binder or polymers each having a functional group which react with each other are bound. In either of the cases, important are kinds of functional groups in the polymer molecule and number thereof.
As an example of these, there has been employed the method in which unsaturated carboxylic acid, unsaturated imide or unsaturated epoxide, or the like are mixed, kneaded to effect reaction. However, in this method, control of numbers of the functional groups which can be introduced in the polymer or kinds thereof is limited.
Also, there have been proposed that various functional groups are introduced by using a phenolic hydroxyl group at the terminal of PPE as a reaction cite. For example, there are a terminal carboxylic acid anhydride modified product as disclosed in Japanese Provisional Patent Publication No. 199754/1988 or Japanese Provisional PCT Publication No. 500456/1987, a terminal alcoholic hydroxy-modified product as disclosed in Japanese Provisional PCT Publication No. 503391/1988, or a terminal glycidyl-modified product as disclosed in U.S. Pat. No. 4,732,937. However, in these polymers, numbers of reaction cites and functional groups are at most one per one polymer molecule so that number of functional group is not in optimum nor satisfied. Also, in Japanese Provisional Patent Publication No. 128056/1988, it has been disclosed that the modified product of PPE using an .alpha.,.beta.-unsaturated carbonyl compound represented by maleic anhydride becomes a compatibilizing agent for a PPE series blended material. In these cases, a content of the maleic anhydride of modified PPE is at most 1% by weight so that such a content is insufficient as a compatibilizing agent.
On the other hand, as an effective method of introducing a functional group, there is a reaction of a boran compound. It has been known that the borane compound can convert into various functional groups with good efficiency by its characteristic reaction. By applying the compound to polymer molecules, it can become an available precursor for functionallized polymer.
These borane compounds can be easily formed by an electrophilic addition reaction of a boron-hydrogen bond to a carbon-carbon unsaturated bond, i.e. the so-called hydroboration reaction. For example, it has been shown that these compounds can be used for converting into many functional groups selectively and good efficiency such as alcoholation (H. C. Brown, Organoboranes in Organic Synthesis, Marcel Dekker (1973)), amination (H. C. Brown, et al., Journal of American Chemical Society, 1964, 86 3565, 1966, 88 2870), esterification (H. C. Brown et al., Journal of American Chemical Society, 1968, 90 818), cyanization (H. C. Brown et al., Journal of American Chemical Society, 1969, 91 6854, 1970, 90 5790) and ketonization (H. C. Brown et al., Journal of American Chemical Society, 1969, 91 6852) and so on.
As for the reaction of the borane compounds as mentioned above, famous research has been carried out in detail by H. C. Brown (H. C. Brown, Organic Synthesis via Branes, John-Wiley (1975), etc.) and applicable range has rapidly been expanded in recent years.
Also, as an effective method of introducing a functional group, there is a reaction of mercaptane having a carbonyl group, hydroxyl group or an alkoxysilyl group. It has been known that these mercaptans are added to a carbon-carbon unsaturated bond with good efficiency mainly by a radical reaction. By applying the compound to a polymer having a carbon-carbon unsaturated bond, functionalization of a polymer can be realized.
However, no report has been made about research in which hydroboration reaction and a subsequent reaction of borane are applied to PPE having an unsaturated bond such as a resin obtained by oxidation polymerization of 2-allyl-6-methylphenol and 2,6-dimethylphenol (for example, U.S. Pat. No. 3,422,062). Further, there is no example that an .alpha.,.beta.-unsaturated carbonyl compound, etc. is reacted to PPE. Further, it has been also not known that the reaction of the above mercaptane is applied to.